163 
resulting from tile draining. The root-habit of the Beech would lead us to 
expect that it would be among the first forms to be affected from this 
change of the water level in the soil. Such an explanation, however, 
would not suffice for the Marshall county case, where the deep rooting 
forms are as seriously affected as the beeches. The part played by the 
other factors mentioned in the production of this forest decay is yet to 
be studied. The subject is of such importance that it will be carefully 
studied before the issuing of the State flora. 
The floral regions of the State as indicated by Coulter and Thomson 
in the “Origin of the Indiana Flora,’* need some modification in the light 
of a more extended knowledge of the flora of the State. The seven floral 
districts of Coulter and Thomson were based largely upon geological hori- 
zons and altitude, factors which are quite subordinate in the limited area 
of Indiana in the determination of plant distribution. The effect of alti- 
tude must be very slight in an area in which the lowlands are about three 
hundred feet above sea level and the highlands only from 900-1,300 feet, 
above. The number of plants whose distribution is limited by geological 
horizons must necessarily be very small in a State so largely affected by 
the drift and in which the amount of soil derived from the country rock 
remaining in situ is so comparatively insignificant. It is not meant that 
these factors may not be of importance in other regions or when wide- 
spread areas are considered, simply that in Indiana they are not domi- 
nant and do not furnish the most natural basis for the division of the 
State into floral districts. Without doubt, within our area, waterways 
furnish the dominant factor in determining plant distribution. That this 
is true can be easily verified by checking the mass distribution of almost 
any abundant form upon a hydrographical map of the State. This is not 
the place to discuss in detail the proposed redistricting of the State, but 
during the coming season outline maps indicating approximately the 
boundaries of the proposed floral regions will be distributed to the work- 
ing botanists of the State for suggestion and criticism. 
The general movement, especially of our summer and fall blooming 
plants is toward the northwest. This was of course to have been ex- 
pected from the direction of the prevailing winds at the time of such dis- 
semination. This movement is quite marked and can be noticed in al- 
most every instance in the, case of plants accidentally introduced into the 
State through the agency of railroads. In the case of the Russian thistle 
*Tndiana Geological Reports, Vol. XIV., p. 255. 
